1. Field of the Invention
The invention is directed to an improved excavator bucket linkage allowing adequate rollback for vertical wall digging and improved bucket curl for truck loading.
2. Description of the Prior Art
Excavators such as backhoes, are work vehicles used for a variety of jobs. An excavator is provided with a pivotal boom to which is attached a pivotal dipperstick. The positions of the boom relative to the vehicle and the dipperstick relative to the boom are controlled by hydraulic cylinders. Typically, a bucket is pivotally attached to the end of the dipperstick remote from the boom. A hydraulic cylinder pivotally attached to the dipperstick is used to position the bucket relative to the dipperstick through a bucket linkage.
A typical bucket linkage is illustrated in US Pat. No. 5,051,057. A binary link extends between the bucket hydraulic cylinder and the bucket. The binary link has a first pivot connection pivotally coupling the binary link to the rod end of the bucket hydraulic cylinder and a second pivot connection pivotally coupling the binary link to the bucket. A follower link extends from the dipperstick to the first pivot connection of the binary link.
Because of interference considerations, forces and velocities at extremes of travel, the bucket is provided with two holes to which the binary link can be pivotally coupled. The first hole allows sufficient rollback to vertical wall digging, and the second hole gives improved truck loading (extreme curled position). In selecting a mode of operation, the operator couples the binary link to one of the two holes.
Another bucket linkage is disclosed in US Pat. No. 4,381,167. This linkage uses four links to improve cutting force at the extreme rollback and extreme curled positions.